1. Field of the Invention
This invention relates to a tube pump suitable as suction means of a discharge recovering apparatus carried on an ink jet recording apparatus for discharging ink from recording means to a recording material to thereby effect recording, a discharge recovering apparatus using the tube pump, and an ink jet recording apparatus provided with the discharge recovering apparatus.
2. Related Background Art
In recent years, the range of use of an ink jet recording apparatus has widened with a rise in its utilization value, and the types of ink jet recording apparatus have been increasing, such as an ink jet recording apparatus characterized by a high quality of photographic image, an ink jet recording apparatus used chiefly for black character recording, which uses a pigment ink for black alone to emphasize the distinctness of black and uses inks of other colors formed of dyes, and further an ink jet recording apparatus characterized by a low price. With the increase in the types of machine, the types of an ink jet recording head as the heart for discharging ink to thereby record an image have also increased, and individual discharge recovering apparatuses corresponding to respective heads have become required, and technical problems to be solved such as poor design efficiency and production efficiency, and a rise in cost resulting therefrom have also arisen.
FIG. 15 of the accompanying drawings is a typical perspective view showing an example of the discharge recovering apparatus of an ink jet recording apparatus according to the prior art, FIG. 16 of the accompanying drawings is a typical perspective view showing an example of the internal structure of the discharge recovering apparatus of FIG. 15, and FIG. 17 of the accompanying drawings is a typical perspective view showing another example of the internal structure of the discharge recovering apparatus of FIG. 15. In FIG. 15, when as the suction means 61 of the discharge recovering apparatus 6, use is made of a tube pump of a type in which a tube disposed along an arcuate guide portion (guide surface) is squeezed by a pressing roller journalled to a rotary member to thereby generate negative pressure (suction force), there is adopted a method of incorporating this tube along the arcuate guide surface by the cooperation thereof with the pressing roller, and this is advantageous for the downsizing of the apparatus and the curtailment of the number of parts, and therefore, a base member (recovering base) for mounting the various parts of the discharge recovering apparatus and the guide portion are constituted by a single part. That is, a construction is adopted in which the guide portion is formed on a portion of the base member of the discharge recovering apparatus.
Some of various ink jet recording heads to which the discharge recovering apparatus imparts the discharge recovering action have various functions as previously described. First, the ink jet recording head carried on the ink jet recording apparatus characterized by the high quality of photographic image is required to minimize the amount of ink discharged from a discharge port, and the opening diameter of the discharge port is a small diameter, and correspondingly thereto, discharge ports are arranged highly densely and the number of the discharge ports is great. Therefore, when in the discharge recovering apparatus, in a capping state in which a cap is brought into close contact with a surface (discharge port surface) formed with a plurality of discharge ports, the interior of the cap is brought into a negative pressure state and ink is drawn out of each discharge port, it is necessary to make great negative pressure act, and a suction pump for generating the great negative pressure becomes necessary. For such a recording head, a tube pump 61 having two lines of tube 616 is connected to a cap 621, as shown in FIG. 16, to thereby make the negative pressure acting on the interior of the cap 621 great.
Also, in the ink jet recording apparatus for effecting chiefly black character recording, which uses a pigment ink for black alone to emphasize the distinctness of black and uses inks of other colors formed of dyes, when suction recovery is to be effected by the discharge recovering apparatus, it is necessary to suck the inks individually so that the pigment and the dyes may not mix with one another. Therefore, a plurality of caps is provided, or a closed space in one cap is divided into two. Such a recording head is handled by using a tube pump 61 having two lines of tubes 616 similar to those in FIG. 16, and divisionally connecting respective ones of the two lines of tubes to two caps 621a and 621b as shown in FIG. 17. By such a contrivance the discharge recovering apparatus corresponding to the aforedescribed two types of recording heads can be made with only the difference in parts between FIG. 16 and FIG. 17, and the mitigation of the poor design efficiency and production efficiency and a rise in cost resulting therefrom is achieved.
However, the aforedescribed ink jet recording apparatus, and the discharge recovering apparatus and the tube pump (pump unit) which are the constituents thereof, have suffered from such technical problems to be solved, as will be described below. That is, in the incorporating of the tubes in the tube pump, there is adopted a method of incorporating the tubes along an arcuate guide surface for crushing the tubes by the cooperation with the pressure roller. However, when the tubes are shifted in an attempt to adjust the mounted positions of the tubes when bringing the tubes along the inner side of the arcuate portion, there occurs the action of the tubes restoring to their straight state, and the tubes have stuck on the guide surface or have floated up from the guide surface and the state of the tubes has not been stable, and the assembling of the tubes has been very difficult. This has resulted in the technical problem that the tubes are liable to be incorporated in a positionally deviated state, a slack state, a buckled state or a twisted state, and erroneous incorporation is liable to occur.
Also, when during the operation of the tube pump, the tubes are pulled by the squeezing action of the pressing roller, it is necessary to fix the mounted position so as not to deviate or come off. Many constituent parts including the tube pump are incorporated in the base member of the discharge recovering apparatus on which the aforementioned guide surface is formed so as to functionally operate, and therefore, a tube fixing portion cannot be disposed in a free space, and it has been difficult to avoid the great deformation of the tubes. If the deformed portions of these tubes exist near the guide surface, when a pump pressure roller rushes into a state opposed to the guide surface, a load suddenly rises, the state opposed to the guide surface is released, there occurs the phenomenon that the pressing roller is pushed out by the elastic force of restitution of the tubes, and the aforementioned rotary member is rotated more rapidly than a driving speed, and this has led to the technical problem that a faulty operation is caused.
Also, the base member on which the various parts of the discharge recovering apparatus are mounted and the aforementioned guide surface are constituted by a single part so as to be advantageous for the downsizing of the apparatus and the curtailment of the number of parts, but since high rigidity and high dimensional accuracy are required of the base member of the discharge recovering apparatus, it is necessary to make the base member by the use of a glass-containing material. Also, in the discharge recovering apparatus of the ink jet recording apparatus according to the prior art, use is made of a construction in which the rotary member is directly rotatably supported by the base member, but the glass-containing material lacks slidability and therefore, when the rotary member is rotated under the great reaction force of the pressure force of the tubes, there arise inconveniences that a great load is produced, the shaving of the material occurs and the shaved powder comes into a sliding portion to thereby cause abnormal sound, and this has led to the technical problem that the application of grease becomes necessary as a countermeasure. In the discharge recovering apparatus, it is required to decrease the application of grease as much as possible from the viewpoint that if the grease adheres to the cap or a wiper, it may close the discharge ports of the recording head.
Also, in recent years, the use of the ink jet recording apparatus has become wider, whereby depending on the use thereof, the types (the diameter and number of the discharge ports) of the recording head with which the discharge recovering apparatus of the ink jet recording apparatus must cope, the kinds of the ink used (dyes, a pigment or a-mixture thereof), and the kinds (construction and number) of ink tanks connected have also continued to increase. If the performance difference required of the suction pump of the discharge recovering apparatus becomes great due to the differences in these types and kinds, it becomes difficult to cope with it by only such tube connecting method as in the aforedescribed example of the prior art, and it becomes necessary to change even the diameter of the tubes of the tube pump and thus, a greatly different discharge recovering apparatus must be newly made.